Power gating technology is usually used in a battery-supplied device or a low leakage-requirement system. A specific circuit can be shut down by turning off one or more power gates on the specific circuit having a circuit state, so as to achieve the purpose of low leakage. However, the circuit state is lost because of cutting off the power supply. The circuit state represented by configuration information is not permitted to be lost because that will cause the configuration information to be absent and cause an unknown status of the specific circuit. Usually, a retention flip-flop (FF) cell is adopted to keep the configuration information indicating the circuit state or configuration, and it cooperates with an additional controller such as a power management unit (PMU) to save and restore. A retention FF cell charges another cost and is only for a specific technology node. This will increase the cost of development and restrict the selection of technology. In addition, the retention FF cell has a larger area and current consumption in a power-on state.
Therefore, it is expected that a novel control module and a method can be adopted to store the configuration information when a system changes from an active mode to an idle mode, and to restore the configuration information when the system changes from the idle mode to the active mode. It is also expected that a novel system structure and a method can be adopted to solve both backup of the configuration information and large area and current consumption.